Mobile communication control method, data communication device, mobile base station, and mobile terminal

Abstract

Disclosed is a technique which reduces the packet loss and the band consumption for data transfer when a mobile terminal conducts the handover between a fixed base station and a mobile base station for group movement. According to this technique, when an MH (mobile terminal) 320 conducts the handover from a fixed base station (E-LSR 230 ) positioned at an edge of an access network 200 to a mobile base station (MEB 310 ) located in a train or the like, a predetermined flag is appended to a frame addressed to the MH in a label switching router (P-LSR 210 ) positioned at a core network 100 side edge of the access network. The frame having the appended flag is copied in the E-LSR 230 . One frame after copied is transmitted directly from the E-LSR to the MH while the other frame after copied is transferred from the E-LSR to the MEB and then transmitted from the MEB to the MH, thus realizing the soft handover.

1 . A mobile communication control method for a mobile communication control system including, in a case in which an access network is formed so that a mobile terminal establishes a connection with a core network, a first edge communication apparatus positioned at an edge of said access network and connected to said core network and a second edge communication apparatus positioned at an edge of said access network and accommodating said mobile terminal, with said mobile terminal accommodated in said second edge communication apparatus being connected through said first edge communication apparatus and said second edge communication apparatus to said core network, comprising:
 a mobile base station accommodating step in which said second edge communication apparatus accommodates a mobile base station capable of accommodating a mobile terminal as its own subordinate;   a connection relation grasping step in which said first edge communication apparatus grasps a connection switching start timing and a connection switching end timing by said mobile terminal which switches a connection between said second edge communication apparatus and said mobile base station;   a flag adding step in which, within a period of time between the connection switching start timing and the connection switching end timing by said mobile terminal, said first edge communication apparatus adds a predetermined flag to a data unit transmitted from an arbitrary communication apparatus, connected to said core network, toward said mobile terminal; and   a data unit duplicating step in which, upon receipt of the data unit having the added predetermined flag, said second edge communication apparatus duplicates the data unit and directly transmits one of the data units, obtained by the duplication, to said mobile terminal serving as its own subordinate while transmitting the other duplicated data unit through said mobile base station to said mobile terminal.   
     
     
         2 . The mobile communication control method according to  claim 1 , further comprising an encapsulation step in which said first edge communication apparatus encapsulates the data unit, addressed to said mobile terminal capable of receiving the data unit through said mobile base station, with a header addressed to said mobile base station,
 wherein, in said data unit duplicating step, upon receipt of the data unit having the added flag, said second edge communication apparatus duplicates the encapsulated data unit and, after decapsulating one of the duplicated data units, transmits the decapsulated data unit directly to said mobile terminal serving as its own subordinate while transmitting the other duplicated data unit directly to said mobile base station.   
     
     
         3 . The mobile communication control method according to  claim 1 , further comprising a data unit transmitting step in which said first edge communication apparatus transmits the data unit, to which the predetermined flag is added in said flag adding step, through a tunnel whose end point is said mobile base station,
 wherein, in said data unit duplicating step, said second edge communication apparatus transfers the data unit having the added predetermined flag and transmitted through said tunnel toward the end point of said tunnel and refers to a destination IP address included in the data unit for transmitting the data unit directly to said mobile terminal serving as its own subordinate.   
     
     
         4 . The mobile communication control method according to  claim 1 , wherein the transfer of the data unit in said access network is made according to a label switching method and, in said access network, the data unit having the added predetermined flag utilizes a path for transfer of a data unit to said mobile base station. 
     
     
         5 . The mobile communication control method according to  claim 4 , wherein, in said flag adding step, the predetermined flag is added to a header for label switching. 
     
     
         6 . A mobile communication control method for a mobile communication control system including, in a case in which an access network is formed so that a mobile terminal establishes a connection with a core network, a first edge communication apparatus positioned at an edge of said access network and connected to said core network and a second edge communication apparatus positioned at an edge of said access network and accommodating said mobile terminal, with said mobile terminal accommodated in said second edge communication apparatus being connected through said first edge communication apparatus and said second edge communication apparatus to said core network, comprising:
 a mobile base station accommodating step in which said second edge communication apparatus accommodates a mobile base station capable of accommodating a mobile terminal as its own subordinate;   a prefix advertising step in which said second edge communication apparatus advertises a prefix identical to a prefix for specifying said access network to its own subordinate;   a common tunnel transferring step in which, in said access network from said first edge communication apparatus to said second edge communication apparatus, said first edge communication apparatus transfers the data unit, which passes through said second edge communication apparatus, through the same tunnel;   a connection relation grasping step in which said second edge communication apparatus grasps a connection switching start timing and a connection switching end timing by said mobile terminal which switches a connection between said second edge communication apparatus and said mobile base station; and   a data unit duplicating step in which, between the connection switching start timing and the connection switching end timing by said mobile terminal, said second edge communication apparatus duplicates the data unit addressed to said mobile terminal and directly transmits one of the duplicated data units to said mobile terminal serving as a subordinate while transmitting the other duplicated data unit through said mobile base station to said mobile terminal.   
     
     
         7 . A data communication device which is in connection with a core network and which is positioned at an edge of an access network for connecting a mobile terminal to said core network, comprising:
 positional information storing means for storing information indicative of positional relationship between an edge communication apparatus positioned at an edge of said access network and capable of accommodating said mobile terminal and a mobile terminal existing under said edge communication apparatus or a mobile base station existing under said edge communication apparatus and capable of accommodating said mobile terminal as its own subordinate;   data unit receiving means for receiving a data unit transmitted from an arbitrary communication apparatus, connected to said core network, to said mobile terminal;   flag adding means for referring to the information indicative of the positional relationship stored in said positional information storing unit to add, to the data unit, a predetermined flag indicative of an instruction for a duplication of the data unit to said edge communication apparatus in a case in which said mobile terminal exists at a position where the data unit is receivable from both said edge communication apparatus and said mobile base station; and   data unit transmitting means for transmitting the data unit, to which the predetermined flag is added by said flag adding means, to said edge communication apparatus.   
     
     
         8 . The data communication device according to  claim 7 , further comprising:
 mobile base station subordinate judging means for referring to the information indicative of the positional relationship stored in said positional information storing unit so as to make a judgment as to whether or not said mobile terminal exists under said mobile base station; and   encapsulation means for, when the judgment by said mobile base station subordinate judging means shows that said mobile terminal exists under said mobile base station, making an encapsulation with a header addressed to said mobile base station.   
     
     
         9 . The data communication device according to  claim 7 , wherein said data unit transmitting means is made to transmit the data unit, to which the predetermined flag is added by said flag adding means, through a tunnel whose end point is said mobile base station. 
     
     
         10 . The data communication device according to  claim 7 , further comprising label adding means for, in a case in which the transfer of the data unit within said access network is made according to a label switching method, adding, to the data unit, a label whereby the data unit is transferred to said edge communication apparatus within said access network. 
     
     
         11 . A data communication device which is positioned at an edge of an access network for connecting a mobile terminal to a core network and which is capable of accommodating said mobile terminal, comprising:
 a mobile base station capable of accommodating said mobile terminal as its own subordinate or radio communication apparatus accommodating means capable of accommodating said mobile terminal;   data unit receiving means for receiving a data unit from said access network:   data duplicating means for, when receiving a data unit to which the predetermined flag to be added when a judgment shows that said mobile terminal exists at a position where the data unit is receivable from both the edge communication apparatus and said mobile base station is added by a data communication device positioned at an edge of said access network and connected to said core network, duplicating the data unit; and   data unit transmitting means for directly transmitting one of the data units obtained by the duplication by said data duplicating means to said mobile terminal serving as its own subordinate and transmitting the other duplicated data unit to said mobile base station.   
     
     
         12 . The data communication device according to  claim 11 , further comprising decapsulation means for, in a state where the data unit having the added predetermined flag is encapsulated with a header addressed to said mobile base station, carrying out a decapsulation on said header addressed to said mobile base station with respect to one of the data units obtained by the duplication by said data duplicating means. 
     
     
         13 . The data communication device according to  claim 11 , wherein the one data unit duplicated by the data duplicating means is transmitted to a destination address specified by the predetermined flag while the other duplicated data unit is transmitted to a destination address derived from a destination IP address included in the data unit. 
     
     
         14 . A mobile base station which is movable and made to carry out the processing on a layer-2 level data unit, comprises:
 radio communication means connectable through radio communication to a base station positioned at an edge of an access network for a connection with a core network;   radio communication apparatus accommodating means capable of accommodating a mobile terminal;   decapsulation means for, when receiving, through said radio communication means, an encapsulated data unit made in a manner such that a data unit addressed to said mobile terminal accommodated in said radio communication apparatus accommodating means is encapsulated with a header addressed to the mobile base station itself, decapsulating the encapsulated data unit; and   data transmitting means for transmitting the data unit, obtained by said decapsulation means and addressed to said mobile terminal, to said mobile terminal.   
     
     
         15 . The mobile base station according to  claim 14 , further comprising beacon transmitting means for transmitting, to a subordinate, a beacon including its own identification information, information indicative of the fact that it is movable and identification information on said base station accommodating it. 
     
     
         16 . A mobile terminal which is movable, comprising:
 radio communication means connectable through radio communication to a base station;   beacon information judging means for, when newly receiving a beacon from a second base station through the use of the radio communication means in a state accommodated in a first base station, referring to identification information on a base station accommodating said second base station, included in the beacon received from said second base station, and making a judgment as to whether or not said first base station and said second base station are identical to each other; and   message transmitting means for, when the judgment in said beacon information judging means shows that said first base station and said second base station are identical to each other, transmitting, to said first base station, a message including its own identification information and identification information on said second base station as a request for allowing a data unit addressed to the mobile terminal to be duplicated in said first base station and receivable from both said first base station and said second base station.